Plug v1.3.0 Plug.Parsers behaviour
A plug for parsing the request body.
This module also specifies a behaviour that all the parsers to be used with Plug should adopt.
Options
:parsers
- a list of modules to be invoked for parsing. These modules need to implement the behaviour outlined in this module.:pass
- an optional list of MIME type strings that are allowed to pass through. Any mime not handled by a parser and not explicitly listed in:pass
willraise UnsupportedMediaTypeError
. For example:["*/*"]
- never raises["text/html", "application/*"]
- doesn’t raise for those values[]
- always raises (default)
All options supported by Plug.Conn.read_body/2
are also supported here (for
example the :length
option which specifies the max body length to read) and
are passed to the underlying call to Plug.Conn.read_body/1
.
This plug also fetches query params in the connection through
Plug.Conn.fetch_query_params/2
.
Once a connection goes through this plug, it will have :body_params
set to
the map of params parsed by one of the parsers listed in :parsers
and
:params
set to the result of merging the :body_params
and :query_params
.
This plug will raise Plug.Parsers.UnsupportedMediaTypeError
by default if
the request cannot be parsed by any of the given types and the MIME type has
not been explicity accepted with the :pass
option.
Plug.Parsers.RequestTooLargeError
will be raised if the request goes over
the given limit.
Parsers may raise a Plug.Parsers.ParseError
if the request has a malformed
body.
This plug only parses the body if the request method is one of the following:
POST
PUT
PATCH
DELETE
For requests with a different request method, this plug will only fetch the query params.
Examples
plug Plug.Parsers, parsers: [:urlencoded, :multipart]
plug Plug.Parsers, parsers: [:urlencoded, :json],
pass: ["text/*"],
json_decoder: Poison
Built-in parsers
Plug ships with the following parsers:
Plug.Parsers.URLENCODED
- parsesapplication/x-www-form-urlencoded
requests (can be used as:urlencoded
as well in the:parsers
option)Plug.Parsers.MULTIPART
- parsesmultipart/form-data
andmultipart/mixed
requests (can be used as:multipart
as well in the:parsers
option)Plug.Parsers.JSON
- parsesapplication/json
requests with the given:json_decoder
(can be used as:json
as well in the:parsers
option)
File handling
If a file is uploaded via any of the parsers, Plug will
stream the uploaded contents to a file in a temporary directory in order to
avoid loading the whole file into memory. For such, the :plug
application
needs to be started in order for file uploads to work. More details on how the
uploaded file is handled can be found in the documentation for Plug.Upload
.
When a file is uploaded, the request parameter that identifies that file will
be a Plug.Upload
struct with information about the uploaded file (e.g.
filename and content type) and about where the file is stored.
The temporary directory where files are streamed to can be customized by
setting the PLUG_TMPDIR
environment variable on the host system. If
PLUG_TMPDIR
isn’t set, Plug will look at some environment
variables which usually hold the value of the system’s temporary directory
(like TMPDIR
or TMP
). If no value is found in any of those variables,
/tmp
is used as a default.
Summary
Callbacks
Attempts to parse the connection’s request body given the content-type type and subtype and the headers
Functions
Callback implementation for Plug.call/2
.
Callback implementation for Plug.init/1
.
Callbacks
parse(conn :: Plug.Conn.t, type :: binary, subtype :: binary, headers :: Keyword.t, opts :: Keyword.t) :: {:ok, Plug.Conn.params, Plug.Conn.t} | {:error, :too_large, Plug.Conn.t} | {:next, Plug.Conn.t}
Attempts to parse the connection’s request body given the content-type type and subtype and the headers.
The arguments are:
- the
Plug.Conn
connection type
, the content-type type (e.g.,"x-sample"
for the"x-sample/json"
content-type)subtype
, the content-type subtype (e.g.,"json"
for the"x-sample/json"
content-type)opts
, the list of options passed to thePlug.Parsers
plug
This function should return:
{:ok, body_params, conn}
if the parser is able to handle the given content-type;body_params
should be a map{:next, conn}
if the next parser should be invoked{:error, :too_large, conn}
if the request goes over the given limit